Merge branch 'single-ca-drv-build' of https://github.com/obsidiansystems/nix

perl/lib/Nix/Store.xs

src/libexpr/get-drvs.cc

src/libexpr/get-drvs.hh

src/libexpr/primops.cc

src/libstore/build.cc

src/libstore/derivations.cc

src/libstore/derivations.hh

src/libstore/local-store.cc

src/libstore/local-store.hh

src/libstore/misc.cc

src/libstore/references.cc

src/libstore/references.hh

src/libstore/store-api.cc

src/libstore/store-api.hh

src/libutil/serialise.hh

src/nix-build/nix-build.cc

src/nix-store/nix-store.cc

src/nix/build.cc

src/nix/command.cc

src/nix/develop.cc